Experimental study on seismic performance of prestressed InorgBam beam-to-column connections

Abstract

Inorganic-bonded bamboo composite (InorgBam) is a novel engineered bamboo product fabricated using bamboo fiber bundles bonded with a magnesium oxysulfide (MOS) inorganic adhesive, thereby providing improved fire resistance, long-term durability, and potential for large cross-sectional structural applications compared with conventional bamboo and timber products. The connection performance of InorgBam structures is crucial for overall safety and post-earthquake recoverability. However, traditional bolted connections often sustain large residual deformations during seismic events. This paper investigates the seismic performance of InorgBam beam-to-column connections incorporating post-tensioned high-strength (HS) steel strands and steel connectors. The effects of different self-centering configurations on seismic performance were experimentally evaluated. The benchmark connection with a Π-shaped slotted-in steel connector exhibited good initial load-carrying capacity but suffered from large residual deformation after cyclic loading, with a relative self-centering capability (RSC) of 0.71. The prestressed connection without effective beam-end confinement experienced brittle splitting failure at the beam end, limiting the activation of the restoring force provided by the HS steel strands. In contrast, the connection combining an external energy-dissipating steel jacket with HS steel strands achieved excellent self-centering performance (RSC = 0.95) and stable energy dissipation. The connection incorporating HS steel strands together with a Π-shaped steel connector and an external steel jacket attained the highest initial stiffness and ultimate load capacity. However, the excessive stiffness restrained rocking behavior and reduced the self-centering capability (RSC = 0.81). Therefore, the enhanced energy-dissipating steel jacket is recommended for self-centering InorgBam beam-to-column connections, as the measure balances ductility, damage control, and self-centering capacity, while avoiding the negative effect of excessive stiffness on the rotational recovery of the connection.